Additively manufactured gearbox with integral heat exchanger

ABSTRACT

A gearbox and a method for additively manufacturing the gearbox are provided. The gearbox includes a housing having an integral heat exchanger additively manufactured within the housing. The heat exchanger includes a plurality of heat exchange passageways for transferring heat between two or more fluids. The heat exchanger is defined at any suitable location or locations within the housing, for example, within voids defined between the walls of the housing and components housed within housing, such as driveshafts, gears, bearings, etc.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 15/375,348,filed on Dec. 12, 2016, titled “ADDITIVELY MANUFACTURED GEARBOX WITHINTEGRAL HEAT EXCHANGER”, which is herein incorporated by reference.

FIELD

The present subject matter relates generally to gearboxes for gasturbine engines, and more particularly, to gearboxes including integralheat exchangers.

BACKGROUND

Heat exchangers may be employed in conjunction with gas turbine enginesfor transferring heat between one or more fluids. For example, a firstfluid at a relatively high temperature may be passed through a firstpassageway, while a second fluid at a relatively low temperature may bepassed through a second passageway. The first and second passageways maybe in contact or close proximity, allowing heat from the first fluid tobe passed to the second fluid. Thus, the temperature of the first fluidmay be decreased and the temperature of the second fluid may beincreased.

Conventional heat exchangers for gas turbine engines are modules or“bricks” that are positioned at various locations within the gas turbineengine. Fluids are supplied to and from the heat exchanger through oneor more fluid circulation conduits. For example, certain gas turbineengines have a heat exchanger for transferring heat from oil heatedwithin an accessory gearbox to fuel that is to be supplied to acombustion section of the gas turbine engine. However, the heatexchanger is located remotely from the accessory gearbox, requiring oiland fuel to be supplied to the heat exchanger through separate fluidcirculation conduits. Each conduit requires additional componentstorage, assembly, and costs. In addition, the likelihood of leaksincreases and significant heat energy may be lost from the fluids asthey are transferred to the remotely located heat exchanger.

Accordingly, a gas turbine engine with an improved heat exchangerconfiguration for cooling oil within a gearbox would be useful. Moreparticularly, a heat exchanger for a gas turbine engine that requiresless space, is easier to assemble and install, and has a reducedlikelihood of fluid leaks and thermal losses would be especiallybeneficial.

BRIEF DESCRIPTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one exemplary embodiment of the present disclosure, a gearboxincluding a housing having a plurality of walls defining an internalchamber is provided. An additively manufactured heat exchanger is formedwithin the chamber on at least one of the plurality of walls, the heatexchanger including a plurality of heat exchange passageways.

In another exemplary aspect of the present disclosure, a method offorming a gearbox is provided. The method includes additivelymanufacturing a heat exchanger onto at least one wall of a gearboxhousing, the heat exchanger including a plurality of heat exchangepassageways.

In still another exemplary aspect of the present disclosure, anadditively manufactured gearbox is provided. The gearbox includes aplurality of chamber walls defining a chamber and one or more gearspositioned within the chamber, a plurality of voids being definedbetween the gears and the chamber walls. At least one heat exchanger isadditively manufactured on the chamber walls to fill at least some ofthe plurality of voids, the heat exchanger including a plurality of heatexchanging walls, at least one of the heat exchanging walls having athickness of less than four millimeters.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures.

FIG. 1 is a schematic cross-sectional view of an exemplary gas turbineengine according to various embodiments of the present subject matter.

FIG. 2 is a perspective view of an accessory gearbox of the exemplarygas turbine engine of FIG. 1 in accordance with an exemplary embodimentof the present disclosure.

FIG. 3 is a cross-sectional view of the exemplary accessory gearbox ofFIG. 2, taken along Line 3-3 of FIG. 2.

FIG. 4 is a cross-sectional view of the exemplary accessory gearbox ofFIG. 2, taken along Line 4-4 of FIG. 2.

FIG. 5 is a perspective view of a heat exchanger configuration that maybe used in the exemplary gearbox of FIG. 2 in accordance with anexemplary embodiment of the present subject matter.

FIG. 6 is a method for forming a gearbox according to an exemplaryembodiment of the present subject matter.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.The terms “upstream” and “downstream” refer to the relative directionwith respect to fluid flow in a fluid pathway. For example, “upstream”refers to the direction from which the fluid flows, and “downstream”refers to the direction to which the fluid flows.

As used herein, a “fluid” may be a gas or a liquid. The present approachis not limited by the types of fluids that are used. In the preferredapplication, the cooling fluid is fuel, and the cooled fluid is oil. Forexample, the oil can be cooled from an initial temperature to adischarge temperature, with the discharge temperature being about 90% ofthe initial temperature or lower (e.g., about 50% to about 90% of theinitial temperature). The present approach may be used for other typesof liquid and gaseous fluids, where the cooled fluid and the coolingfluid are the same fluids or different fluids. Other examples of thecooled fluid and the cooling fluid include air, hydraulic fluid,combustion gas, refrigerant, refrigerant mixtures, dielectric fluid forcooling avionics or other aircraft electronic systems, water,water-based compounds, water mixed with antifreeze additives (e.g.,alcohol or glycol compounds), and any other organic or inorganic heattransfer fluid or fluid blends capable of persistent heat transport atelevated or reduced temperature.

An additively manufactured gearbox is generally provided along with amethod for additively manufacturing such a gearbox. The gearbox includesa housing having an integral heat exchanger including a plurality ofheat exchange passageways for transferring heat between two or morefluids. The heat exchanger is defined at any suitable location orlocations within the housing, for example, within voids defined betweenthe walls of the housing and components housed within housing, such asdriveshafts, gears, bearings, etc.

Referring now to the drawings, FIG. 1 is a schematic cross-sectionalview of a gas turbine engine in accordance with an exemplary embodimentof the present disclosure. More particularly, for the embodiment of FIG.1, the gas turbine engine is a high-bypass turbofan jet engine 10,referred to herein as “turbofan engine 10.” As shown in FIG. 1, theturbofan engine 10 defines an axial direction A (extending parallel to alongitudinal centerline or central axis 12 provided for reference) and aradial direction R. In general, the turbofan 10 includes a fan section14 and a core turbine engine 16 disposed downstream from the fan section14.

The exemplary core turbine engine 16 depicted generally includes asubstantially tubular outer casing 18 that defines an annular inlet 20.The outer casing 18 encases, in serial flow relationship, a compressorsection including a booster or low pressure (LP) compressor 22 and ahigh pressure (HP) compressor 24; a combustor or combustion section 26;a turbine section including a high pressure (HP) turbine 28 and a lowpressure (LP) turbine 30; and a jet exhaust nozzle section 32. A highpressure (HP) shaft or spool 34 drivingly connects the HP turbine 28 tothe HP compressor 24. A low pressure (LP) shaft or spool 36 drivinglyconnects the LP turbine 30 to the LP compressor 22.

For the embodiment depicted, the fan section 14 includes a variablepitch fan 38 having a plurality of fan blades 40 coupled to a disk 42 ina spaced apart manner. As depicted, the fan blades 40 extend outwardlyfrom disk 42 generally along the radial direction R. Each fan blade 40is rotatable relative to the disk 42 about a pitch axis P by virtue ofthe fan blades 40 being operatively coupled to a suitable actuationmember 44 configured to collectively vary the pitch of the fan blades 40in unison. The fan blades 40, disk 42, and actuation member 44 aretogether rotatable about the longitudinal axis 12 by LP shaft 36 acrossa power gear box 46. The power gear box 46 includes a plurality of gearsfor stepping down the rotational speed of the LP shaft 36 to a moreefficient rotational fan speed and is attached to one or both of a coreframe or a fan frame through one or more coupling systems.

Referring still to the exemplary embodiment of FIG. 1, the disk 42 iscovered by rotatable front hub 48 aerodynamically contoured to promotean airflow through the plurality of fan blades 40. Additionally, theexemplary fan section 14 includes an annular fan casing or outer nacelle50 that circumferentially surrounds the fan 38 and/or at least a portionof the core turbine engine 16. It should be appreciated that the nacelle50 may be configured to be supported relative to the core turbine engine16 by a plurality of circumferentially-spaced outlet guide vanes 52.Moreover, a downstream section 54 of the nacelle 50 may extend over anouter portion of the core turbine engine 16 so as to define a bypassairflow passage 56 therebetween.

During operation of the turbofan engine 10, a volume of air 58 entersthe turbofan 10 through an associated inlet 60 of the nacelle 50 and/orfan section 14. As the volume of air 58 passes across the fan blades 40,a first portion of the air 58 as indicated by arrows 62 is directed orrouted into the bypass airflow passage 56 and a second portion of theair 58 as indicated by arrow 64 is directed or routed into the LPcompressor 22. The ratio between the first portion of air 62 and thesecond portion of air 64 is commonly known as a bypass ratio. Thepressure of the second portion of air 64 is then increased as it isrouted through the high pressure (HP) compressor 24 and into thecombustion section 26, where it is mixed with fuel and burned to providecombustion gases 66.

The combustion gases 66 are routed through the HP turbine 28 where aportion of thermal and/or kinetic energy from the combustion gases 66 isextracted via sequential stages of HP turbine stator vanes 68 that arecoupled to the outer casing 18 and HP turbine rotor blades 70 that arecoupled to the HP shaft or spool 34, thus causing the HP shaft or spool34 to rotate, thereby supporting operation of the HP compressor 24. Thecombustion gases 66 are then routed through the LP turbine 30 where asecond portion of thermal and kinetic energy is extracted from thecombustion gases 66 via sequential stages of LP turbine stator vanes 72that are coupled to the outer casing 18 and LP turbine rotor blades 74that are coupled to the LP shaft or spool 36, thus causing the LP shaftor spool 36 to rotate, thereby supporting operation of the LP compressor22 and/or rotation of the fan 38.

The combustion gases 66 are subsequently routed through the jet exhaustnozzle section 32 of the core turbine engine 16 to provide propulsivethrust. Simultaneously, the pressure of the first portion of air 62 issubstantially increased as the first portion of air 62 is routed throughthe bypass airflow passage 56 before it is exhausted from a fan nozzleexhaust section 76 of the turbofan 10, also providing propulsive thrust.The HP turbine 28, the LP turbine 30, and the jet exhaust nozzle section32 at least partially define a hot gas path 78 for routing thecombustion gases 66 through the core turbine engine 16.

It should be appreciated that the exemplary turbofan 10 depicted in FIG.1 is by way of example only and that in other exemplary embodiments,turbofan 10 may have any other suitable configuration. For example, itshould be appreciated that in other exemplary embodiments, turbofan 10may instead be configured as any other suitable turbine engine, such asa turboprop engine, turbojet engine, internal combustion engine, etc.

Referring still to FIG. 1, turbofan 10 may further include an accessorygearbox 100. Accessory gearbox 100 is generally configured forsupporting operation of various accessory systems of turbofan 10 or anassociated aircraft by harnessing power from the HP spool 34 or LP spool36 through an input shaft 102, as described below. Although thedescription below refers to the construction of accessory gearbox 100,it should be appreciated that accessory gearbox 100 is used only for thepurpose of explaining aspects of the present subject matter. Theconcepts disclosed herein could be similarly applied to other gearboxes,such as a transfer gear box, power gear box 46, a reduction gearbox, orto any other component of turbofan 10. Indeed, aspects of the presentsubject matter may be applied to form components used in automotive,aviation, maritime, and other industries to assist in heat transferbetween fluids.

Referring now to FIGS. 2 through 5, accessory gearbox 100 will bedescribed according to an exemplary embodiment of the present subjectmatter. More specifically, FIG. 2 provides a perspective view ofaccessory gearbox 100, while FIGS. 3 and 4 provide cross sectional viewsof accessory gearbox 100 taken along Lines 3-3 and 4-4, respectively, ofFIG. 2. FIG. 5 provides an exemplary heat exchanging structure thatcould be integrally formed within accessory gearbox 100 according to anexemplary embodiment of the present subject matter. It should beappreciated that accessory gearbox 100 and the associated heatexchanging structure are described herein only for the purpose ofexplaining aspects of the present subject matter. Variations andmodifications may be made to the heat exchanging structure, which may beused within any suitable component of any suitable machine while stillremaining within the scope of the present subject matter.

Referring now to FIG. 2, accessory gearbox 100 includes a housing 110having a plurality of walls 112. More specifically, walls 112collectively define an internal chamber 114 of accessory gearbox 100which may house a plurality of gears, driveshafts, bearings, and one ormore heat exchangers or heat exchanging surfaces, as will be describedbelow. Input shaft 102 may extend from the core engine (e.g., from HPspool 34 of turbofan 10) into accessory gearbox 100 and may be rotatablycoupled to a gear train or assembly (not shown) for driving variousaccessory systems. More specifically, housing 110 may define an inputport 116 through which input shaft 102 extends into internal chamber 114in a fluid tight manner for transmitting rotational force to the geartrain.

Housing 110 of accessory gearbox 100 may further define a plurality ofoutput ports 118 for receiving output shafts (not shown). The outputshafts are operably coupled with the input shaft 102 through the geartrain and are configured for transmitting rotational power to accessorysystems of turbofan 10 or another suitable device. For example, inputshaft 102 may be configured for transferring rotational power from theHP spool 34 to rotate drive gears and driveshafts for a fuel pump, ahydraulic pump, or any other suitable accessory system. Accessorygearbox 100 may further include any suitable fluid seals, bearings, orother support structures to allow input shaft 102 and output shafts torotate freely and in a fluid tight manner.

Notably, the gear train and housing 110 generate a significant amount ofheat during operation due to the interaction and friction between thevarious gears, shafts, bearings, etc. To provide lubrication and reduceheat generation, oil is contained within internal chamber 114. It isoften desirable to transfer heat from the oil within accessory gearbox100 to a separate, second fluid. Reducing the temperature of the oilextends the life of the oil and of the components, e.g., gears, which itlubricates. In addition, heat from the oil may be transferred to thesecond fluid for useful purposes.

Conventional methods of reducing the temperature of oil within anaccessory gearbox include pumping the oil from a chamber of the gearboxthrough a fluid conduit to an external heat exchanger. The heatexchanger passes a second flow of cooling fluid, e.g., fuel, through aseparate channel or passageway through the heat exchanger. Therelatively hot oil and the relatively cool fuel is in thermalcommunication as they are passed through the heat exchanger, such thatheat is transferred from the relatively hot oil to the relatively coolfuel. The cooled oil is then circulated back through the chamber of thegearbox and the process continues.

However, as explained above, the remote positioning of theseconventional heat exchanging modules requires additional housing spacewithin the gas turbine engine. In addition, fluids must be circulatedthrough separate fluid circulation conduits that must be assembled usingseals, bolts, nuts, etc. Thus, each conduit requires additionalcomponent storage, assembly, and costs. In addition, the likelihood ofleaks increases and significant heat energy may be lost from the fluidsas they are transferred to the remotely located heat exchanger.Therefore, the present subject matter provides a more efficient and lesscomplicated way of cooling oil within an accessory gearbox withoutexpanding the footprint of the previously existing gearbox. Although theheat exchanging configuration described herein contemplates cooling ofan oil stream (e.g., the hot stream) with a fuel stream (e.g., the coldstream), the heat exchanger configuration is broadly applicable to avariety of heat exchanger applications involving multiple fluid types.

Referring now to FIG. 3, a heat exchanger 130 may be incorporated intoaccessory gearbox 100 for exchanging heat between two or more fluids.For example, heat exchanger 130 may be formed within internal chamber114 on at least one of walls 112 and may define multiple passagewaysthat pass a relatively hot fluid and a relatively cool fluid forexchanging heat between the two fluids. Notably, heat exchanger 130 ispositioned within internal chamber 114 in a void that is defined betweenthe wall 112 of the chamber and the gears, shafts, bearings, etc. ofaccessory gearbox 100. As illustrated, heat exchanger 130 extends onlyalong a bottom of housing 110. However, it should be appreciated thataccording to alternative embodiments, heat exchanger 130 may bepositioned at any suitable location or locations within accessorygearbox 110. For example, if accessory gearbox 100 maintains the samefootprint as prior gearboxes, heat exchangers 130 could fill some or allvoids within internal chamber 114 of accessory gearbox 100.Alternatively, walls 112 of housing 110 could be thinned or thefootprint of accessory gearbox 100 could be expanded to accommodateadditional heat exchanger areas within accessory gearbox 100.

Referring now additionally to FIG. 5, an exemplary heat exchanger 130will be described. Heat exchanger 130 may, according to someembodiments, be used in accessory gearbox 100. Notably, FIG. 5illustrates an exemplary segment of heat exchanger 130 for the purposeof explaining its general operation, but the size, shape, andconfiguration of heat exchanger 130 is not intended to limit the scopeof the present subject matter. For example, the size, shape, number, andconfiguration of fluid passageways may be varied while remaining withinthe scope of the present subject matter.

According to the illustrated embodiment, heat exchanger 130 includes aplurality of first fluid passageways 132 and a plurality of second fluidpassageways 134. First and second fluid passageways 132, 134 are inthermal communication with each other for transferring heat between thefluids passing therethrough. Notably, however, first fluid passageways132 and second fluid passageways 134 are separated from each other inthat the respective fluids do not physically mix with each other. Inthis regard, each of first fluid passageways 132 and second fluidpassageways 134 may be separated by a plurality of heat exchanger walls136.

First fluid passageway 132 and second fluid passageway 134 generallydefine non-circular geometries, so as to increase the surface areaavailable for thermal exchange. For example, according to theillustrated embodiment, first fluid passageway 132 and second fluidpassageway 134 have a square cross-section. In this regard, each fluidpassageway 132, 134 may have a height 138 that is defined as the averagedistance between the walls 136 that define the respective fluidpassageway 132, 134. The additive manufacturing methods described belowenable the formation of such fluid passageways 132, 134 at any suitableheight. For example, according to one embodiment, height 138 is aboutfifteen millimeters. However, it should be appreciated, that first fluidpassageway 132 and second fluid passageway 134 may have any suitablesize and geometry. It should be appreciated, that as used herein, termsof approximation, such as “approximately,” “substantially,” or “about,”refer to being within a ten percent margin of error.

Each of first fluid passageway 132 and second fluid passageway 134 maybe straight, curvilinear, serpentine, helical, sinusoidal, or any othersuitable shape. For example, as illustrated in FIG. 5, first fluidpassageway 132 is curvilinear. Notably, heat exchanger 130 may generallyinclude performance-enhancing geometries and heat exchanging featureswhose practical implementations are facilitated by an additivemanufacturing process, as described below. For example, according tosome exemplary embodiments, first fluid passageway 132 and second fluidpassageway 134 may have a plurality of heat exchanges surfaces orfeatures, e.g., fins (not shown), to assist with the heat transferprocess.

First fluid passageways 132 may be configured for receiving a firstfluid, e.g., oil. Similarly, second fluid passageways 134 may beconfigured for receiving a second fluid, e.g., fuel. However, it shouldbe appreciated that any suitable fluids may be used in the heat transferprocess. For example, air, fuel, oil, refrigerant, or any other suitablefluid may be used in the heat transfer process. In addition, heatexchanger 130 may be configured for having more than two fluidpassageways.

According to the illustrated embodiment, first fluid passageway 132 andsecond fluid passageways 134 are configured in a cross-flowconfiguration, i.e., the oil and fuel flow perpendicular to each other.However, it should be appreciated that first fluid passageway 132 andsecond fluid passageway 134 could alternatively be configured in acounter-flow configuration, where heat exchanger 130 is designed suchthat the first fluid passageway 132 and second fluid passageway 134 aresubstantially parallel and the respective fluid streams travel inopposite directions in their respective passageways 132, 134. Inaddition, according to some embodiments, the fluids may travel in thesame direction in their respective passageways 132, 134.

Referring again to FIGS. 2 through 4, accessory gearbox 100 may furtherdefine various fluid supply or circulation conduits for passing thevarious fluids to and within accessory gearbox 100. For example,according to the illustrated embodiment, housing 110 defines an oilsupply conduit 140 and a fuel supply conduit 142 for supplying oil andfuel to the first fluid passageways 132 and second fluid passageways134, respectively. Oil supply conduit 140 and fuel supply conduit 142may be integrally formed, e.g., via additive manufacturing, withinhousing 110 and may extend between different sections of internalchamber 114 or may extend outside of accessory gearbox 100 to externalreservoirs. In this regard, for example, oil supply conduit 140 mayextend to an oil reservoir or to a sump within accessory gearbox 100. Anoil pump may be operably coupled to the oil supply conduit 140 forcirculating oil through accessory gearbox 100 and first fluidpassageways 132. Similarly, fuel supply conduit 142 may extend to a fuelsupply and a fuel pump can circulate fresh fuel into heat exchanger 130.After heat is transferred from the oil to the fuel, the fuel may bepassed through fuel supply conduit 142 out of accessory gearbox 100,e.g., to combustion section 26 of turbofan 10.

The various portions of accessory gearbox 100 may be constructed usingany suitable material, in any suitable geometry, density, and thickness,as needed to provide necessary structural support to accessory gearbox100. For example, external walls 112 accessory gearbox 100 may be formedfrom a rigid, thermally insulating material. In addition, walls 112 maybe thicker and denser to provide structural support for loadsexperienced by accessory gearbox 100 during mounting, assembly, andoperation of gas turbine engine 100. By contrast, internal walls (e.g.,walls 136 of heat exchange passageways 132, 134) may be thinner andconstructed of a more thermally conductive material in order to enhanceheat transfer. For example, according to an exemplary embodiment, wallsof the heat exchange passageways 132, 134 may be constructed of athermally conductive metal alloy and may be less than ten millimetersthick. According to still another exemplary embodiment, walls of heatexchange passageways may be less than four millimeters thick and mayvary depending on the what fluid will be passed through the passageway.

Similarly, various surfaces within housing 110 may be constructed toprovide structural support, e.g., by using a stronger material and/orincreased density of a specific region to improve its structuralcapabilities. For example, according to one embodiment, one or moreload-bearing surfaces 150 may be additively manufactured through amiddle of heat exchanger 130 for providing structural support toaccessory gearbox 100. Load-bearing surfaces 150 may be used to providestructural rigidity to housing 110 or to support components withinaccessory gearbox 100, such as a drive shaft or bearings.

Now that the construction and configuration of accessory gearbox 100 andheat exchanger 130 according to an exemplary embodiment of the presentsubject matter has been presented, an exemplary method 200 for forming agearbox according to an exemplary embodiment of the present subjectmatter is provided. Method 200 can be used to form accessory gearbox100, or any other suitable gearbox with an integral heat exchanger. Itshould be appreciated that the exemplary method 200 is discussed hereinonly to describe exemplary aspects of the present subject matter, and isnot intended to be limiting.

Referring now to FIG. 6, method 200 includes, at step 210, additivelymanufacturing a gearbox housing having a plurality of walls defining aninternal chamber. Step 220 includes additively manufacturing a heatexchanger onto at least one of the plurality of walls of the gearboxhousing. The heat exchanger is formed such that it includes a pluralityof heat exchange passageways for passing one or more fluids. The gearboxhousing and heat exchanger may be formed using the same or differentmaterials. According to the illustrated exemplary embodiment, thegearbox housing and heat exchanger are formed integrally using additivemanufacturing and a single material. According to alternativeembodiments, however, the gearbox housing may instead be machined orcast prior to additively manufacturing the heat exchanger thereon.Method 200 further includes, at step 230, additively manufacturing atleast one fluid supply conduit for providing fluid communication betweena fluid supply and at least one of the plurality of heat exchangepassageways of the heat exchanger. The fluid supply may be, for example,a fuel reservoir, and fuel from the reservoir may be passed through theheat exchanger to extract heat from the oil prior to passing onto acombustion section of a gas turbine engine.

In general, the disclosed accessory gearbox 100 may be manufactured orformed using any suitable process. However, in accordance with severalaspects of the present subject matter, accessory gearbox 100 may beformed using an additive-manufacturing process, such as a 3-D printingprocess. The use of such a process may allow accessory gearbox 100 to beformed with an integral heat exchanger, as described above according toan exemplary embodiment. In other words, the heat exchanger may beformed as an integral structure within the gearbox. In particular, themanufacturing process may allow accessory gearbox 130 to be integrallyformed and include a variety of features not possible when using priormanufacturing methods. Some of these novel features will be describedbelow.

As used herein, the terms “additively manufactured” or “additivemanufacturing techniques or processes” refer generally to manufacturingprocesses wherein successive layers of material(s) are provided on eachother to “build-up”, layer-by-layer, a three-dimensional component. Thesuccessive layers generally fuse together to form a monolithic componentwhich may have a variety of integral sub-components. Although additivemanufacturing technology is described herein as enabling fabrication ofcomplex objects by building objects point-by-point, layer-by-layer,typically in a vertical direction, other methods of fabrication arepossible and within the scope of the present subject matter. Forexample, although the discussion herein refers to the addition ofmaterial to form successive layers, one skilled in the art willappreciate that the methods and structures disclosed herein may bepracticed with any additive manufacturing technique or manufacturingtechnology. For example, embodiments of the present invention may uselayer-additive processes, layer-subtractive processes, or hybridprocesses.

Suitable additive manufacturing techniques in accordance with thepresent disclosure include, for example, Fused Deposition Modeling(FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjetsand laserjets, Sterolithography (SLA), Direct Selective Laser Sintering(DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM),Laser Engineered Net Shaping (LENS), Laser Net Shape Manufacturing(LNSM), Direct Metal Deposition (DMD), Digital Light Processing (DLP),Direct Metal Laser Sintering (DMLS), and other known processes.

The additive manufacturing processes described herein may be used forforming components using any suitable material. For example, thematerial may be plastic, metal, concrete, ceramic, polymer, epoxy,photopolymer resin, or any other suitable material that may be in solid,liquid, powder, sheet material, wire, or any other suitable form. Morespecifically, according to exemplary embodiments of the present subjectmatter, accessory gearbox 100 may be formed in part, in whole, or insome combination of materials including but not limited to pure metals,nickel alloys, chrome alloys, titanium, titanium alloys, magnesium,magnesium alloys, aluminum, aluminum alloys, and austenite alloys suchas nickel-chromium-based superalloys (e.g., those available under thename Inconel® available from Special Metals Corporation).

In addition, one skilled in the art will appreciate that a variety ofmaterials and methods for bonding those materials may be used and arecontemplated as within the scope of the present disclosure. As usedherein, references to “fusing” may refer to any suitable process forcreating a bonded layer of any of the above materials. For example, ifan object is made from polymer, fusing may refer to creating a thermosetbond between polymer materials. If the object is epoxy, the bond may beformed by a crosslinking process. If the material is ceramic, the bondmay be formed by a sintering process. If the material is powdered metal,the bond may be formed by a melting process. One skilled in the art willappreciate other methods of fusing materials to make a component byadditive manufacturing are possible, and the presently disclosed subjectmatter may be practiced with those methods.

In addition, the additive manufacturing process disclosed herein allowsa single component to be formed from multiple materials. Thus, accessorygearbox 100 may be formed from any suitable mixtures of the abovematerials. For example, a component may include multiple layers,segments, or parts that are formed using different materials, processes,and/or on different additive manufacturing machines. In this manner,components may be constructed which have different materials andmaterial properties for meeting the demands of any particularapplication. In addition, although accessory gearbox 100 is describedabove as being constructed entirely by additive manufacturing processes,it should be appreciated that in alternate embodiments, all or a portionof accessory gearbox 100 may be formed via casting, machining, and/orany other suitable manufacturing process. Indeed, any suitablecombination of materials and manufacturing methods may be used to formaccessory gearbox 100.

An exemplary additive manufacturing process will now be described.Additive manufacturing processes fabricate components usingthree-dimensional (3D) information, for example a three-dimensionalcomputer model, of the component. Accordingly, a three-dimensionaldesign model of accessory gearbox 100 may be defined prior tomanufacturing. In this regard, a model or prototype of accessory gearbox100 may be scanned to determine the three-dimensional information ofaccessory gearbox 100. As another example, a model of accessory gearbox100 may be constructed using a suitable computer aided design (CAD)program to define the three-dimensional design model of accessorygearbox 100.

The design model may include 3D numeric coordinates of the entireconfiguration of the component including both external and internalsurfaces of accessory gearbox 100. For example, the design model maydefine the housing, the heat exchanging structure, internal fluidchannels or circulation conduits, openings, support structures, etc. Inone exemplary embodiment, the three-dimensional design model isconverted into a plurality of slices or segments, e.g., along a central(e.g., vertical) axis of the component or any other suitable axis. Eachslice may define a two-dimensional (2D) cross section of the componentfor a predetermined height of the slice. The plurality of successive 2Dcross-sectional slices together form the 3D component. The component isthen “built-up” slice-by-slice, or layer-by-layer, until finished.

In this manner, accessory gearbox 100 is fabricated using the additiveprocess, or more specifically each layer is successively formed, e.g.,by fusing or polymerizing a plastic using laser energy or heat or bysintering metal powder. For example, a particular type of additivemanufacturing process may use an energy beam, for example, an electronbeam or electromagnetic radiation such as a laser beam, to sinter ormelt a powder material. Any suitable laser and laser parameters may beused, including considerations with respect to power, laser beam spotsize, and scanning velocity. The build material may be formed by anysuitable powder or material selected for enhanced strength, durability,and useful life, particularly at high temperatures.

Each successive layer may be, for example, between about 10 μm and 200μm, although the thickness may be selected based on any number ofparameters and may be any suitable size according to alternativeembodiments. Therefore, utilizing the additive formation methodsdescribed above, the heat exchanging surfaces (e.g., walls 136) may beas thin as one thickness of an associated powder layer, e.g., 10 μm,utilized during the additive formation process. However, according tothe exemplary embodiment, walls 136 of the heat exchanger may be formedat less than fifteen millimeters thick. According to still anotherexemplary embodiment, walls 136 may be less than five millimeters thick.

Notably, in exemplary embodiments, several features of accessory gearbox100 are formed integrally with walls 112 of accessory gearbox 100 andmay be made from the same material or a different material. Suchconstruction of accessory gearbox 100 and heat exchanger 130 haspreviously not been possible due to manufacturing restraints. However,the present inventors have advantageously utilized current advances inadditive manufacturing techniques to develop exemplary embodiments ofaccessory gearbox 100 generally in accordance with the presentdisclosure. While the present disclosure is not limited to the use ofadditive manufacturing to form accessory gearbox 100 generally, additivemanufacturing does provide a variety of manufacturing advantages,including ease of manufacturing, reduced cost, greater accuracy, etc.

In this regard, utilizing additive manufacturing methods, accessorygearbox 100 may be a single piece of continuous plastic, and may thusinclude fewer components and/or joints than known gearboxes. Theintegral formation of accessory gearbox 100 through additivemanufacturing may advantageously improve the overall assembly process.For example, the integral formation reduces the number of separate partsthat must be assembled, thus reducing associated time and overallassembly costs. Additionally, existing issues with, for example,leakage, joint quality between separate parts, and overall performancemay advantageously be reduced.

Also, the additive manufacturing methods described above enable muchmore complex and intricate shapes and contours of accessory gearbox 100.For example, heat exchanger 130 may include thin walls (less thanfifteen millimeters), narrow passageways, and novel heat exchangingfeatures. All of these features may be relatively complex and intricatefor maximizing heat transfer and minimizing the size or footprint ofheat exchanger 130. In addition, the additive manufacturing processenables the manufacture of structures having different materials,specific heat transfer coefficients, or desired surface textures, e.g.,that enhance or restrict fluid flow through a passageway. Thesuccessive, additive nature of the manufacturing process enables theconstruction of these passages and features. As a result, heat exchanger130 performance may be improved relative to other accessory gearboxeswith separate, dedicated heat exchanger assemblies.

Utilizing an additive process, the surface finish and passageway sizemay be formed to improve fluid flow through the passageways, to improveheat transfer within the passageways, etc. For example, the surfacefinish may be adjusted (e.g., made smoother or rougher) by selectingappropriate laser parameters during the additive process. A rougherfinish may be achieved by increasing laser scan speed or a thickness ofthe powder layer, and a smoother finish may be achieved by decreasinglaser scan speed or the thickness of the powder layer. The scanningpattern and/or laser power can also be changed to change the surfacefinish in a selected area. Notably, a smoother surface may promote afaster flow of fluid through a heat exchanger passageway, while arougher surface may promote turbulent flow of fluid and increased heattransfer.

The discussion above describes accessory gearbox 100 and its method ofconstruction. However, it should be appreciated that aspects of thepresent subject matter may be used to manufacture a gearbox having anintegral heat exchanger for use with any other suitable device orsystem. For instance, the gearbox may be an accessory gear box, atransfer gear box, a reduction gearbox, or any other suitable gearboxfor a gas turbine engine. Indeed, aspects of the present subject mattermay be used to incorporate heat exchangers into any component where voidspace is available and high temperature gradients may be used totransfer heat energy.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A gearbox comprising: a housing comprising aplurality of walls defining an internal chamber; and an additivelymanufactured heat exchanger formed within the chamber on at least one ofthe plurality of walls, the heat exchanger comprising a plurality ofheat exchange passageways.
 2. The gearbox of claim 1, wherein thehousing and the heat exchanger are additively manufactured as a single,integral piece.
 3. The gearbox of claim 2, wherein the housing isadditively manufactured using a first material and the heat exchanger isadditively manufactured using a second material, the second materialbeing different from the first material.
 4. The gearbox of claim 1,wherein a wall of the heat exchanger has a thickness of less than fourmillimeters.
 5. The gearbox of claim 1, further comprising at least oneadditively manufactured fluid supply conduit, the fluid supply conduitproviding fluid communication between a fluid supply and at least one ofthe plurality of heat exchange passageways of the heat exchanger.
 6. Thegearbox of claim 6, wherein the fluid supply is located outside of thehousing of the gearbox.
 7. The gearbox of claim 1, wherein the pluralityof heat exchange passageways comprise a plurality of first heat exchangepassageways that are configured for receiving air, fuel, or oil, and aplurality of second heat exchange passageways that are configured forreceiving air, fuel, or oil.
 8. The gearbox of claim 7, wherein thefirst heat exchange passageways and the second heat exchange passagewaysare configured in a cross-flow, counter-flow, or parallel-flowarrangement.
 9. The gearbox of claim 1, wherein at least a portion ofthe heat exchanger is used as a load bearing surface.
 10. The gearbox ofclaim 1, wherein the gearbox is an accessory gearbox or a transfergearbox of a gas turbine engine.
 11. A method of forming a gearbox, themethod comprising: additively manufacturing a heat exchanger onto atleast one wall of a gearbox housing, the heat exchanger comprising aplurality of heat exchange passageways.
 12. The method of claim 11,further comprising additively manufacturing the gearbox housing.
 13. Themethod of claim 11, wherein the gearbox housing and the heat exchangerare additively manufactured as a single, integral piece.
 14. The methodof claim 11, wherein the gearbox housing is additively manufacturedusing a first material and the heat exchanger is additively manufacturedusing a second material, the second material being different from thefirst material.
 15. The method of claim 11, wherein a wall of the heatexchanger has a thickness of less than four millimeters.
 16. The methodof claim 11, further comprising additively manufacturing at least onefluid supply conduit, the fluid supply conduit providing fluidcommunication between a fluid supply and at least one of the pluralityof heat exchange passageways of the heat exchanger, wherein the fluidsupply is located outside of the gearbox housing.
 17. An additivelymanufactured gearbox comprising: a plurality of chamber walls defining achamber; one or more gears positioned within the chamber, a plurality ofvoids being defined between the gears and the chamber walls; and atleast one heat exchanger additively manufactured on the chamber walls tofill at least some of the plurality of voids, the heat exchangercomprising a plurality of heat exchanging walls, at least one of theheat exchanging walls having a thickness of less than four millimeters.18. The additively manufactured gearbox of claim 17, wherein the chamberwalls and the heat exchanger are additively manufactured as a single,integral piece.
 19. The additively manufactured gearbox of claim 18,wherein the chamber walls are additively manufactured using a firstmaterial and the heat exchanger is additively manufactured using asecond material, the second material being different from the firstmaterial.
 20. The additively manufactured gearbox of claim 17, furthercomprising at least one additively manufactured fluid supply conduit,the fluid supply conduit providing fluid communication between a fluidsupply located outside the chamber and the heat exchanger.